Clamping arrangement for high voltage bushing



J. MEZZACK March 17, 1959 CLAMPING ARRANGEMENT FOR HIGH VOLTAGE BUSHING Filed May 25, 1957 In enffir Jose p/z .Mezzack, EM/r CLAMPING ARRANGEMENT FOR HIGH VOLTAGE BUSHING Joseph Mezzack, Pittsfield, Mass., assignor to General Electric Company, a corporation of New York Application May 23, 1957, Serial No. 661,145 Claims. (Cl. 174-167) This invention relates to a high voltage electrical insulating bushing, and more in particular to an improved arrangement for clamping the central conductor to the insulating shell of a high voltage electrical insulating bushing.

Electrical insulating bushings of one type are comprised of a hollow cylindrical insulating shell through which a central conductor extends. The central conductor, which may be hollow, is provided with terminal fittings on either end, the terminals being soldered or otherwise permanently affixed to the central conductor. One of the terminal fittings usually has a diameter larger than that of the central conductor, and is provided with a gasketed surface that engages one end of the insulating shell.

In order to facilitate assembly of the bushing, the terminal fitting at the other end of the central conductor has a smaller diameter than the inside diameter of the insulating shell, so that the insulating shell may he slipped over this end of the central conductor. In order to apply clamping pressure to the insulating shell, the end of the central conductor having the smaller diameter terminal fitting has been generally provided with external threads, and a nut threaded over the end of the central conductor held the insulating shell in place.

While this arrangement has been satisfactory for bushings having small sized central conductors, it has been found to be uneconomical to manufacture where thecentral conductor is a large sized tube or red, since special equipment must be provided to form the threads of the conductor and nut for each different size of central conductor.

It is therefore an object of this invention to provide an improved clamping arrangement for clamping the central conductor to the insulating shell of a high voltage electrical insulating bushing.

,It is a further object to provide a clamping arrangement for clamping the central conductor to the insulating shell of a high voltage electrical insulating bushing, the clamping arrangement being characterized by not requiring the central conductor to be threaded.

Briefly stated, in accordance with one aspect of my invention I provide means for clamping one end of the insulating shell to the central conductor of a high voltage electrical insulating bushing of the type including a cylindrical insulating shell having a central conductor extending axially therethrough. The conductor has a portion fixed with respect to the shell, and one end of the conductor extends'beyon'd .one end of the insulating shell. The clamping means comprises annular gland means surrounding the central conductor and engaging the end of the insulating shell. The gland serves as a seal between the conductor and shell. Annular plate means are provided surrounding the conductor between the end of the shell and the end of the conductor, and resilient means such as springs are provided extending between the plate means and gland means. An annular groove is provided United States Patent 0 ice in the conductor adjacent the end thereof, and a split ring is provided in the groove. A plurality of bolt means are arranged to communicate axial clamping pressure between the plate and ring means, and thence to the end of the insulating shell by way of the resilient means and gland means.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which I regard as my invention, it is believed that the invention will be better understood from the following description taken in connection with the accompanying drawing.

In the drawing:

Fig. 1 is a partially cross-sectional view of a high voltage electrical insulating bushing embodying the clamping arrangement of my invention, the central portion of the bushing being omitted for the sake of clarity,

Fig. 2 is an enlarged cross-sectional view of a portion of the bushing of Fig. l, and

Fig. 3 is a bottom view of the bushing of Fig. l and illustrating the relative positions of the cross-sectional views of Figs. 1 and 2.

Referring now to the drawing, and more particularly to Fig. l, therein is illustrated a high voltage electrical insulating bushing comprising a hollow cylindrical insulating shell 10, such as a ceramic shell. A cylindrical central conductor 11 is provided extending axially through the shell 10, one end 12 of the central conductor 11 extending beyond one end 13 of the insulating shell. While the central conductor 11 is illustrated as being hollow, it is obvious that it may also be comprised of a solid rod.

A terminal fitting 14 is brazed or otherwise rigidly electrically afiixed to. the upper end of the central conductor, and the terminal assembly 14 has a radially outwardly extending flange 15 that engages axially the upper end 16 of the insulating shell 10. Another terminal assembly 17 is brazed or otherwise rigidly affixed to the lower end 12 of the central conductor, the terminal assembly 17 having a diameter less than the internal diameter of the shell 10.

A gland assembly 20 is provided on the lower end 13 of the shell 10, the gland assembly comprising an annular plate 21 surrounding the central conductor, an annular gasket 22 between the plate 21 and the shell 10, and an annular gasket 23 contacting the central conductor and held in place between the plate 21 and another annular plate 24.

Spring retaining means 30 comprising a pair of annular plates 31 and 32 in face to face relation are disposed about the central conductor 10 between the end 13 of the shell and the end 12 of the conductor. The plate 31 of the spring retaining means faces the gland means 20, and is provided with a plurality of apertures 33 (see Figs. 2 and 3). A plurality of helical springs 34 are provided extending from the apertures 33 into contacting relationship with the plate 24 of the gland means 20.

An annular groove 40 is provided on the external surface of the central conductor 11 adjacent the lower end 12, and split ring members 41 are positioned in the groove. A plurality of bolts 42 extending between the spring retaining means 30 and the split rings 41 are threaded in apertures 43 in the plate 32 and have heads extending into counterbored portions 44 of apertures 45 in the split rings 41. The bolts 42 are preferably of the hexagon socket cap screw type so that they may be turned by a wrench extending through the apertures 45 in the split rings. Apertures 46 are provided in the plate 31 so that the threaded ends of the bolts may extend therethrough.

The bushing may be mounted by any conventional means, such as a mounting flange (not shown) cemented to the central portion of the insulating shell.

In the assembly of the bushing of my invention, the insulating shell is first slipped over the central conductor so that the upper end thereof engages the flange of the upper terminal fitting. Then the gland assembly is fit over the central conductor so that the gasket 22 engages the lower end of the insulating shell and the spring retaining means is next slipped over the lower end of the central conductor, and the springs assembled extending from the apertures 33 and engaging the plate 24 of the gland means 20. The bolts 42 are threaded in the plates 32 far enough to permit assembly of the split rings in the groove 40, and then the bolts are backed off, as by a wrench extending through the apertures 45, so that the heads of the bolts engage the shoulders of the counterbored portions 44 of apertures 45. Then clamping pressure is applied to the spring retaining means by external means, such as a hydraulic jack, and the bolts are backed off again to engage the shoulders of the counterbored portions of the apertures 45. When the external pressure is removed, the clamping pressure is maintained by engagement of the split ring with the shoulder of the groove 40 adjacent the end of the central conductor. The clamping pressure is communicated to the lower end of the insulating shell by way of the gland means, spring retaining means, springs, and bolts. The use of external clamping pressure during assembly eliminates the possibility that the threads of the bolts may be stripped if the bolts are backed off under pressure.

It will be understood, of course, that while the form of the invention herein shown and described constitutes the preferred embodiment of my invention, it is not intended herein to illustrate all of the possible equivalent forms or ramifications thereof. It will also be understood that the words employed are words of description rather than of limitation, and that various changes may be made without departing from the spirit or scope of the invention herein disclosed. Thus reference to the lower and upper ends of the bushing components is purely descriptive, and not intended to designate any particular position in which the bushing may be mounted. It is aimed in the appended claims to cover all such changes as may fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a high voltage electrical insulating bushing of the type including cylindrical insulating shell means having a central conductor extending axially therethrough, said conductor having a portion fixed with respect to said shell means and having one end extending beyond one end of said shell means, means for clamping said end of said shell means to said conductor comprising annular gland means slidably surrounding said conductor and engaging said end of said shell means, annular plate means surrounding said conductor, resilient means extending between said plate means and gland means, an annular groove in said conductor, split ring means in said groove, and bolt means arranged to communicate axial clamping pressure between said plate and ring means.

2. In a high voltage electrical insulating bushing of the type including a cylindrical insulating shell having a cylindrical central conductor extending axially therethrough, said conductor having a portion fixed with respect to said shell means and having one end extending beyond one end of said shell means, means for clamping said end of said shell to said conductor comprising annular gland means slidably surrounding said conductor and axially engaging said one end of said shell, said gland means providing a seal between said shell and conductor, annular spring retaining means surrounding said conductor, a plurality of spring means extending between said gland means and retaining means, an annular groove in said conductor adjacent said one end thereof, split ring means in said groove, and bolt means arranged to communicate axial clamping pressure between said ring means and retaining means.

3. In a high voltage electrical insulating bushing of the type including a cylindrical insulating shell having a cylindrical central conductor extending axially therethrough, said conductor having a portion fixed with respect to said shell means and having one end extending beyond one end of said shell means, means for clamping said end of said shell to said conductor com prising annular gland means slidably surrounding said conductor and axially engaging said one end of said shell, said gland means providing a seal between said shell and conductor, annular spring retaining means slidably surrounding said conductor between said gland means and said one end of said conductor, a plurality of spring means extending between said retaining means and gland means, an annular groove in said conductor adjacent said one end thereof, split ring means in said groove engaging the shoulder thereof toward said one end of said conductor, and bolt means extending axially between said retaining means and ring means.

4. In a high voltage electrical insulating bushing of the type including a cylindrical insulating shell having a cylindrical central conductor extending axially therethrough, said conductor having a portion fixed with respect to said shell means and having one end extending beyond one end of said shell means, means for clamping said end of said shell to said conductor comprising annular gland means slidably surrounding said conductor and axially engaging said one end of said shell, said gland means providing a seal between said shell and conductor, annular spring retaining means slidably surrounding said conductor between said gland means and said one end of said conductor, a plurality of spring means extending axially between said retaining means and gland means, an annular groove in said conductor adjacent said one end thereof, split ring means in said groove engaging the shoulder thereof toward said one end of said conductor, a plurality of recesses circumferentially spaced on said ring means, and a plurality of bolt means threaded in said retaining means, said bolt means having ends extending into said recesses of said ring means.

5. In a high voltage electrical insulating bushing of the type including a cylindrical insulating shell having a cylindrical central conductor extending axially therethrough, said conductor having one end extending beyond one end of said shell and the other end fixed with respect to the other end of said shell, means for clamping said one end of said shell to said conductor comprising annular gland means slidably surrounding said conductor and axially engaging said one end of said shell, said gland means providing a seal between said shell and conductor, annular spring retaining means slidably surrounding said conductor between said gland means and said one end of said conductor, a plurality of helical springs extending axially between said gland means and said retaining means, an annular groove in said conductor adjacent one end thereof, split ring means in said groove engaging the shoulder thereof adjacent said one end of said conductor, a plurality of counterbored apertures in said ring means, and a plurality of bolts threaded in said retaining means, said bolts having heads extending into the counterbores of said apertures to communicate clamping pressure from said ring means to said retaining means and, via said springs, to said gland means.

References Cited in the tile of this patent UNITED STATES PATENTS 

